Microreactor systems are typically used to measure catalytic activity. One conventional type of microreactor system is a pulse unit. A pulse unit is one in which a micro or nano scale reaction sample is injected into a micro or nano scale type of chemical reaction unit which contains a catalyst. Upon contact with the catalyst, the reactant is converted into a chemical reaction product, and the product is sent to an analyzer for analysis.
A pulse unit typically includes a syringe type of injector for injecting the chemical reactant into the unit. In order to transport the reactant into the reaction chamber where the catalyst is located, a carrier gas is used. The carrier gas is essentially operated as a steady flow of inert gas that is in fluid communication with the catalyst in the reaction chamber. As the carrier gas flows through the reaction chamber, the reactant is injected by the syringe into a common conduit with the carrier gas, and the carrier gas transports the reactant to the reaction zone for contact with the catalyst. This type of injection process is referred to as a pulse technique, since only pulses of reactant can be injected into the reaction chamber, as opposed to a steady or continuous flow of reactant at a known concentration.
UK Patent Application GB 2 124 369 A discloses a pulse type of microreactor system. The system is provided for use in refining, petrochemistry, treatment of synthesis gas or fine chemistry. The system includes a fixed bed catalyst reactor, means for injecting a charge of material into the reactor with the aid of a carrier gas, a furnace capable of heating to a range of from 50° C. to 300° C., a plurality of sampling valves, and means for analyzing reaction product.
A problem with pulse type microreaction units is generally that it is difficult to control reaction conditions such that various reaction parameters can be studied with reliable accuracy. For example, kinetic studies require that pressure and conversion be easily controlled and monitored. In units such as pulse units, reaction pressure and conversion is not easily controlled due to the pulse type nature of the reactant being pushed through a conversion catalyst. If one is trying to measure, for example, kinetics at less than 100% conversion, one may have to use many pulses as an estimate of the catalyst activity. This is because a typical pulse quantity of reactant encountering fresh catalyst will typically have 100% conversion due to the micro or nano scale quantity of the pulse sample that is typically injected into the reaction unit. It is, therefore, desirable to find reaction units, particularly micro scale or nano scale injection units, which are suitable for kinetic studies.